Research
Mapping Biodiversity in Central America
Abstract
Measuring biodiversity of large areas, such as entire countries or regions, is a difficult and costly process. One largely untapped and potentially useful source of biodiversity information is museum collection databases. But how does one from a large database of collection records to a succinct description of biodiversity? This paper describes a number of ArcView GIS scripts that use a museum database to generate biodiversity information such as species per area counts, area-species curves, endemicity plots, and species contours representing Central American freshwater fish.
Introduction
A key to understanding the diversity, evolution and biogeography of organisms within any landscape is a spatial database of distribution of its component species. This data is gathered in the field and the collections are often passed onto museums for cataloguing and storage. Thus museum collection databases should be a key resource for studies in biodiversity. The goal of our research is to gain an understanding of the diversity, evolution and biogeography of freshwater fish in Panama and the rest of Central America. To this end, we embarked upon assembling a GIS database of freshwater fish collection activity, as reflected in museum holdings. From an appropriate summary and exploratory analysis of this database we hoped to gain the answers to questions such as:
- What species of freshwater fish are found in Central America?
- What is the relative abundance of these species within this area?
- Can the landscape be divided into biogeographic regions based on similarities and distinctiveness of their faunal assemblages?
- What historic and evolutionary factors can explain the current distribution of freshwater fish in Central America?
- How does genetic data about the structure of populations within this landscape inform the studies described above?
This last question is directly related to our studies in the molecular phylogeography of freshwater fish using DNA sequence information (Bermingham & Martin, 1998; Martin & Bermingham, 1998). As a desirable spin-off gained with very little additional effort, we endeavored to collect and summarize information useful in the conservation biology of the area of study. Some of these data are:
- Identifying species-rich regions within the area of study.
- Document and describe the current fauna and its distribution.
- Describe the range and habitat of species endemic to drainages in Central America.
The GIS database product that would be formed in the course of study would, we believe, serve as a resource to other ichthyologists and evolutionary biologists (not to mention any other specialist with an interest in the data). It is our intention to provide access to this GIS database through the Internet as map-serving technology makes this possible.
Our study focuses on lower Central America (Photo credit: National Geographic Maps: Physical map of the World). This is described as the land area bordered by Lake Nicaragua in the north and the Cordillera Occidental (NW Colombia) in the south. These two natural features form vicariant barriers that would make the landscape between them a separate biogeographic region for freshwater fish within the neotropics.
The region is of interest because:
- It is the northern part of the neotropics that connects to the Neartic zone in North America - a biogeographic region with a quite different freshwater fish faunal assemblage.
- About 3 million years ago the isthmus of Panama reconnected North and South America after ~50 million years making this isthmus a relatively young land mass making this a laboratory in which to observe the evolutionary processes of speciation, extinction and dispersal (Stehli & Webb, 1985).
- The rising of the isthmus led to the Great American Interchange - a mass migration of animals and plants between the tropics and the temperate latitudes (Bussing, 1985).
- To understand the evolution and biogeography of freshwater fish in this region, it is necessary to understand its community ecology